Abstract:This report is the second report in a series of reports which describe a new and unique approach for modeling either narrowband or wideband high frequency (HF) channels. Although narrowband models of the HF channel have existed for many years, they are applicable to only a limited set of actual narrowband propagation conditions. The need for an HF channel model that is valid for both narrow and wide bandwidths over a more extensive range of propagation conditions motivated the research documented in this series of reports.
The reports in this series describe the development of a channel transfer function for the HF channel that accurately models a wide variety of propagation conditions and can be used for the evaluation of either narrowband or wideband HF systems. Part I of this series of reports described the development of a model that represents the median channel conditions. The present report, Part II of the series, describes the stochastic portion of the model which simulates the time–varying distortion of a transmitted signal due to dispersion, scattering due to irregularities in the ionosphere, Doppler spread and Doppler shift. The development of the stochastic model is described. The model output is compared with measured propagation data obtained on a variety of HF links. The mechanism for this comparison is the channel scattering function which has been found to be an excellent descriptor of the time–varying dispersive HF channel.

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